This application claims the priority of German Patent Document No. 101 24 864.4, filed May 22, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a gearbox housing element and to a method for acting upon the oil level of a gearbox.
German Patent Document DE 196 44 738 A1 of the generic type discloses a device for regulating the oil level in an automatic gearbox. The device has an upper opening which can be adjusted in height to a small extent and by means of which the height of an oil level can be predetermined. If, for example during a filling process, the oil level exceeds the height of the upper opening, oil emerges through the upper opening and out of the gearbox housing, from an oil outlet opening, until the oil level corresponds to the oil level predetermined by the height of the upper opening.
Special features for draining or exchanging the oil are not to be found in the prior art forming the generic type. It is known therefrom to remove an entire oil sump together with the oil disposed therein from the gearbox housing, in which case great care has to be taken during the removal and transportation of the oil sump in order to avoid the oil escaping. As an alternative, the arrangement of a separate oil drain plug is known which, however, demands an increased outlay on design and construction space, an increased weight and an increase of necessary sealing points to the outside.
Taking this as the starting point, the present invention provides a gearbox housing element and a method by means of which simplified drainage or exchange of oil is permitted with simple regulation of the height of the oil level.
In a first working position, which corresponds, for example, to a (permanent) operating position and/or a filling position, the upper opening predetermines the height of an oil level. In this connection, the upper opening can be arranged at a predetermined fixed height. As an alternative, the height of the upper opening can be adjusted according to an operating parameter, such as the temperature of the gearbox oil, in particular in accordance with one of the embodiments according to German Patent Document DE 196 44 738 A1, the disclosure of which is expressly incorporated by reference herein.
The device can be brought into a second working position for the at least partial emptying of the oil volume from the gearbox housing. In this position, the oil can be drained via an oil drain opening of the device, which opening is arranged below the upper opening. The volume of the oil which can be emptied is correlated here with the difference in the heights of the upper opening and the oil drain opening provided. According to the invention, before the oil sump is removed, oil can be drained through the oil drain opening, as the result of which the process of removing the oil sump and of removing the oil from the latter is decisively simplified. At the same time, the necessity of a separate oil drain plug and the provision of further sensitive sealing points are superfluous. If the oil drain opening is arranged at the lowest point of the oil sump, the gearbox oil can be virtually completely emptied before the oil sump is removed.
An advantageous feature of the gearbox housing element according to the invention includes a mechanical action upon the device that takes place from the lower side of the gearbox or the oil sump through the oil outlet opening. This mechanical action is used to bring the device from the first working position into the second working position, i.e., the oil drain opening arranged below the upper opening is created. For example, the oil drain opening is formed with apertures which are closed in the first working position, and in the second working position create a connecting duct between the internal volume of the oil sump and the oil outlet opening, through which duct the oil can emerge in order to drain the volume. The oil outlet opening can be formed, for example, by a (rotary) sliding valve. Accordingly, the upper opening and the oil drain opening are formed by different parts or subregions of the device. In the second working position, the upper opening can furthermore be opened or else closed.
In accordance with an embodiment of the gearbox housing element according to the invention, in the first working position part of the device has a tight connection to the oil drain opening. This tight connection can be released by the mechanical action, for example of a suitably designed tool, in order to produce the second working position by releasing the oil drain opening. The mechanical action in particular causes the part of the device which is arranged above the oil drain opening to be released from the gearbox housing, so that only the oil drain opening, which is opened in the second working position, is present and creates a connection of the internal volume of the oil sump to the oil outlet opening.
The device is preferably formed with a snap-in pipe. The snap-in pipe is connected to the gearbox housing. The connection is undertaken here by a snap-in process which involves a form-fitting engagement which can be released by snapping in or elastic deformations of the components involved. The use of a snap-in pipe of this type enables the gearbox housing element according to the invention to be designed in a particularly simple manner.
The present invention also includes a method for acting upon the liquid level of a gearbox, in which when the gearbox is being filled with oil or during operation of the gearbox, an upper opening of a device, which forms a connecting duct to the surroundings, predetermines the height of an oil level of the gearbox. In order to drain the oil, a tool enters into the oil outlet opening (which is still closed) from the lower side of the gearbox and acts mechanically upon the device in such a manner that an oil drain opening of the device, which opening is arranged below the upper opening, is created in order to empty the oil volume. The gearbox oil can be drained before the oil sump is removed, in which case the provision of a separate oil drain plug is superfluous. The method according to the invention can be carried out in a particularly simple, clean and rapid manner.
Two preferred exemplary embodiments of the device according to the invention will be explained in greater detail below with reference to the drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.